A twelve-lead electrocardiogram has become a widely used non-invasive standard in diagnosing heart diseases, such as ischemic heart disease and acute myocardial infarction.
FIG. 1 illustrates a conventional twelve-lead electrocardiogram system for a human body. In the conventional twelve-lead electrocardiogram system, ten electrodes (RL, LL, RA, LA, V1-V6) are attached to the surface of the human body, wherein the electrodes (V1-V6) are positioned on the chest of the human body, and the electrodes (RL, LL, RA, LA) are positioned on the limbs of the human body. The electrode (RL) is used as a reference ground, and heart potentials (vF, vR, vL, v1-v6) sensed respectively by the electrodes (LL, RA, RL, V1-V6) are input to an apparatus 200, namely an electrocardiograph. The apparatus 200 produces twelve-lead electrocardiogram that includes six waveforms of limb leads, named as I, II, III, aVR, aVL and aVF, and six waveforms of chest leads, named as V1, V2, V3, V4, V5 and V6, with the following definitions.
TABLE 1LeadDefinitionIvL − vRIIvF − vRIIIvF − vLaVRvR − (vL + vF)/2aVLvL − (vR + vF)/2aVFvF − (vL + vR)/2V1v1 − (vR + vL + vF)/3V2v2 − (vR + vL + vF)/3V3v3 − (vR + vL + vF)/3V4v4 − (vR + vL + vF)/3V5v5 − (vR + vL + vF)/3V6v6 − (vR + vL + vF)/3
The leads (I, II, V1-V6) are regarded as independent leads, and the leads (III, aVR, aVL, aVF) are regarded as non-independent leads.
However, mounting and maintaining attachment of such ten electrodes (RL, LL, RA, LA, V1-V6) to record the twelve-lead electrocardiogram are almost impractical. For a patient, it is very difficult to do this for long-term bedside monitoring because the number of the electrodes (RL, LL, RA, LA, V1-V6) and the conventional configuration severely restrict the mobility of the patient.